Hospital bed

ABSTRACT

A PAIR OF ADJUSTABLE SPRING ELEMENTS, HAVING TRAVELING MEANS, ARE CONNECTED BETWEEN A CHASSIS AND MATTRESS SUPPORT WHEREIN SAID TRAVELING MEANS MOVE IN AN ARCUATE PATH TO RAISE OR LOWER SAID MATTRESS SUPPORT.

1971 J. N. J. VAN DER'TMEIJ 3,626,522

HOSPITAL BED 2 Sheets-Sheet 2 Filed Sept, 22, 1969 United States Patent 3,626,522 HOSPITAL BED Johannes N. J. van der Meij, Hobbemalaan 7, Hilversum, Netherlands Filed Sept. 22, 1969, Ser. No. 859,916 Int. Cl. A61g 7/00 US. Cl. -63 5 Claims ABSTRACT OF THE DISCLOSURE A pair of adjustable spring elements, having traveling means, are connected between a chassis and mattress support wherein said traveling means move in an arcuate path to raise or lower said mattress support.

This invention relates to a vertically adjustable hospital bed of the kind having a chassis supported on the ground, and a mattress frame movable relative to said chassis in a path located in a vertical plane under guidance from guiding mechanism. One disadvantage of these known kinds of hospital beds which are adjustable by hand or foot is that either the entire energy for raising the weight of the bed plus the patient must be provided by the operator or, if there is weight compensation by means of springs, no allowance is made for different weights of patients, which may be widely different indeed.

The object of the present invention is to provide a vertically adjustable bed which does not have the above drawbacks and can be rapidly adjusted to the desired height by hand or foot with a minimum amount of energy.

To that effect, according to the invention, the upward movement of the mattress frame is effected by the resultant force of at least two spring elements, the line of action of at least one of said spring elements about one point of suspension of the spring element being so adjustable as regards its direction that the other point of suspension of the spring element describes a path having substantially the form of an arc of a circle having its centre in the first-mentioned point of suspension. It is thus achieved that the weight of the bed and the patient can be compensated for any Weight of the patient without any appreciable work having to be performed, so that a nurse can adjust the bed to the desired height without any trouble and in a rapid Way.

In a preferred embodiment of the invention, the path of adjustment of the adjustable spring element is so located that the action of the other spring or springs is promoted in one part of the path of adjustment and counteracted in the other part of the path of adjustment. In this way a large range of compensation can be obtained, while it is possible to use lighter springs than if a compensating spring should provide the force available for lifting the bed exclusively by counteracting the non-adjustable spring.

In a certain position of the mattress frame, for which, for reasons to be explained hereinafter, the lowermost position can be selected, the adjustable spring element will not become longer or shorter during the adjustment of its point of suspension along a circular path as described, whereas the resultant force required for adjusting the height of the mattress frame is yet changed as a result of the changed position of the line of action of the spring element. Consequently, the operator only needs to provide the frictional energy of the adjustment mechanism to give the bed with the patient a weight compensation accurately adapted to the patients weight.

The compensating mechanism according to the invention can be given an extremely simple embodiment if the guiding mechanism comprises carrying rods pivoting to the mattress frame in a vertical plane and having their other ends guided in the chassis for horizontal sliding and pivoting movement, said carrying rods being halfway their length, measured between the axes of the pivot points, pivoted to an arm which has its other end pivoted to a fixed point of the chassis vertically below the upper pivot point and in alignment with the sliding path of the lower pivot point of the carrying rod. Preferably such a carrying rod is provided adjacent each corner of the mattress frame, the horizontal sliding movements of the lower pivot points of the carrying rods taking place in pairs simultaneously and to the same extent, but in opposite directions by means of a rigid structure for each pair of carrying rods, said rigid structures pivoted to the lower pivots of said carrying rods and guided for horizontal slid ing movement in the chassis, which structures keep the carrying rods pairwise in parallel relationship to each other in all positions, and are each pivoted to a crankshaft extending towards the centre of the chassis, which crankshafts have their other ends symmetrically pivoted to a rocker member suspended for rocking movement about a fixed point of the chassis. Acting on said rocker member are then at least one non-adjustable spring and at least one adjustable spring.

One embodiment of the invention will be described, by way of example, with reference to the accompanying drawings. 'In said drawings,

FIG. 1 is a vertical longitudinal sectional view of the hospital bed according to the invention;

FIG. 2 is a plan view of the chassis on the line IIlI of FIG. 1, some parts being omitted for clarity.

As shown, the hospital bed according to the invention is built up from a chassis 1 and a mattress frame 2, interconnected by four carrying rods 3, 4, 5 and 6, the rods 3 and 5 being pivoted to a rigidified structure 7 mounted for horizontal sliding movement in the chassis 1, and the carrying rods 4 and 6 being similarly pivoted to the structure 8. The upper ends of the carrying rods 3, 4, 5 and 6 are pivoted to the corner points of the mattress frame 2. Furthermore, each carrying rod 3, 4, 5 and 6 is guided at a point located midway between its pivoting ends in an arcuate track, the centre of curvature of which is vertically below the upper pivot point and in alignment with the trajectory of the lower pivot point of the carrying rod. By virtue of this kinematic arrangement, which is otherwise of known kind, the upper pivot point of each carrying rod describes a straight, vertical path. The movements of the structures 7 and 8 are synchronised by means of a crank-driveshaft mechanism comprising a rocker member 9 and two crankshafts 10 and 11, providing a pivot connection between the rocker member 9 and the structure 7, and between the rocker member 9 and the structure 8, so that the mattress frame is maintained in a horizontal position without the occurrence of torsional forces.

The rocker member 9 is driven by a tension spring 12 which has its non-moving end pivoted to the chassis 1. Acting on the other side of the rocker member '9 is a tension spring 13, which has its fixed end likewise pivoted to the chassis 1, and its moving other end pivoted to a sliding block 14., adapted to move in an arc of a circle. In the position of the rocker member 9 shown in FIG. 2, the mattress frame is in its lowermost position. In this position, the centre of the arc described by the groove 15 is in the pivot point 16 of the tension spring 13. In the position as shown the springs 12 and 13 tend to rotate the rocker member 9 in the same sense. If, however, the sliding member 14 has moved to the part 15' of the guide track 15 located on the other side of the pivot of the rocker member 9, the spring 13 will counteract the action of the spring 12. The strengths of the springs 12 and 13 have been so selected that for the maximum weight of the mattress frame plus the patient the two springs should be in the position as shown, while for the minimum weight, i.e. for the mattress frame (plus bed) without the patient, the adjustable spring 13 should be in the dot-dash position. To illustrate this by means of a numerical example, let it be assumed that the empty bed, i.e. the mattress frame plus the mattress and the bed weighs 20 kg, while the patients weight can range up to maximum 120 kg. Assuming further, for the purposes of this example, a constant ratio of 1:1 between, on the one hand, the trajectories of the pivot point 17 of the spring 12 and the pivot point 18 of the spring 13 in the two extreme positions, and, on the other, the vertical path of the mattress frame 2, a tensional force of approximately 80 kg. may be selected for the spring 12 and a tensional force of approximately 60 kg. for the spring 13.

In one extreme position 18 the mattress frame will then receive a upward force of 140 kg., and in the other extreme position 18 of the spring 13 the mattress frame will be subjected to an upward force of 20 kg. In the intermediate positions of the sliding block 14, the upward force on the mattress frame ranges from 20 to 140 kg.

The adjustment of the line of action of the spring 13 is effected as follows.

Secured to the sliding member 14 is a cable 19 arranged to pull the sliding member back and forth along the guide track 15. The cable 19 is passed over sheaves 20 extending obliquely through the rocker member 8, so that the part of the cable 19 extending along the concave wall of the guide track extends via pulleys to the bottom side of the rocker member 9. The parts 22 of the cable 19 located below the rocker member 9 are passed via a pulley 23, mounted for rotation in the chassis at a fixed point, to the shorter end 24 of the chassis, whence they pass via guide rollers 25 to a Windlass 26 connected with a handwheel 27. By rotating the handwheel 27, the operator can displace the sliding member 14 in the guide track 15, thereby adjusting the line of action of the spring 13, with the above-described effect regarding the resultant force on the rocker member 9. The location of the pulley 23 is such that the parts 22 of the cable 19 approximately intersect the axis of rotation of the rocker member 9. It is thus achieved that when the rocker member 9 is moved the position of the cable relative to the guide track 15 is not appreciably changed.

The rocker member 9 is journalled in the chassis 1 by means of integral trunnions 30 and 31, the trunnion 31 being secured to the rocker member 9 by means of a bracket 32, the trunnions 30 and 31 being journalled in cross-strips 34 and 35 constituting part of the construction of the fixed chassis 1.

Arranged on the cross-strip 35 is a pin 36 on which the pulley 23 can freely rotate. The spring 13 can be combined with a hydraulic cylinder Whose oil circuit is throttled for limiting the rate of elevation or lowering of the mattress frame 2, and which can be locked through a rod system by means of a brake pedal (not shown), so that the movement of the rocker member 9 and hence any position of the mattress frame can be fixed.

The operation of the hospital bed according to the invention is as follows:

It is assumed that the rocker member has the position shown in FIG. 2, i.e. the mattress frame with the bed in the lowermost position, and the spring 13 in the dotdash position. The brake is applied. Now a patient is placed on the bed. The operator releases the brake and operates the handwheel 27 to displace the sliding member 14 and thereby adjust the line of action of the spring 13 to the position of the spring 13 shown in full lines in FIG. 2. During this movement the counteraction of the spring 13 on the action of the spring 12 is progressively decreased, so that the resultant torque on the rocker member 9 tending to raise the mattress frame is gradually increased.

Consequently, as the brake is released, the bed will begin to rise at a certain moment. The operator then releases the handwheel, waits until the bed has reached its uppermost position, and then applies the brake. After the patient has been attended to by the nurse, the brake is again released, and the handwheel is turned in the opposite direction by a small increment. The mechanism then becomes under-compensated and the bed will be lowered to its lowermost position. It will be clear that operating the handwheel only requires a minimum of energy, while in the position shown in full lines the displacement of the line of action of the spring 13 only requires the energy needed to overcome the friction of the mechanism, and in the dot-dash position of the guide track the displacement of the line of action over a short path in the direction of the dot-dash position of the spring requires the energy to overcome the friction plus a certain amount of energy to extend the spring, which is caused by the fact that in the dotted position the centre of the arcuate track of the guide member is no longer located in the axis of the pivot 16.

If so desired, it can be ensured that there is a smaller difference in energy required to operate the handwheel in the fully drawn position and in the dot-dash position of the guide track, which can be achieved by providing that the position of the guide track 15 in which its centre is located on the axis of the pivot 16 is intermediate the fully-drawn and the dot-dash positions of the guide track 15.

It should be noted that, although the invention has been described with particular reference to a vertically adjustable hospital bed, it may also offer a solution for all kinds of problems of vertical adjustment approximately identical to those of a vertical adjustable hospital bed.

I claim:

1. A hospital bed with a vertically adjustable mattresssupporting frame comprising, a chassis, a mattress-supporting frame, mechanism for raising and lowering the mattress-supporting frame comprising a rockable member connected to said frame and said chassis, means pivotally mounting said rockable member on said chassis, at a fixed pivot point, a pair of spring elements coactive with each other and said rockable member to raise and lower said frame, means connecting one spring to a fixed point on said chassis and means connecting said one spring element to another fixed point on said rockable member, pivot means connecting the other spring element to a fixed point on said chassis and travelling means movably connecting said other spring element to said rockable member, means to move said travelling means to opposite sides of said fixed pivot point of said rockable member along an arcuate path constituting an arc of a circle centered at said pivot means to apply a rotative moment to said rockable member with said spring elements coacting in applying a rotative force in a common direction of rotation and for moving said travelling means to a point on said path at which forces applied by said spring element are in opposition, means guiding said travelling means for travel on said path effecting increasing of rotational moment applied by said spring elements upon travel of said travelling means in one direction and decreasing the moment as said travelling member is moved in an opposite direction toward said one point at which the forces of said spring elements are in opposition, and said mechanism comprising support rods free to travel at one end on said chassis for lifting and lowering said frame vertically While holding said frame in a horizontal position.

2. A hospital bed according to claim 1, including means rockably mounting said rockable member secured to said chassis.

3. A hospital bed according to claim 1, in which said means guiding said rockable member comprises part of said rockable member having a groove defining said arcuate path along which said travelling means travels.

4. A hospital bed according to claim 1, including means loading the rockable member with a load moment developed by the mattress-supporting frame and a load thereon, said load moment being opposite to the moment applied to said rockable member by said spring elements.

5. A hospital bed according to claim 1, in which said means to move said travelling means comprises a manually operated crank for moving said rockable member symmetrically about fixed pivot point of said rockable memher.

References Cited UNITED STATES PATENTS 710,697 10/1902 Koch 563 UX 5 2,523,076 9/ 1950 Sweetland 5- 63 2,873,455 2/1959 Davis 5-63 3,271,795 9/1966 Hillenbrand et a1. 563

10 PAUL R. GILLIAM, Primary Examiner 

